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Flashing Lights & Floating Spots: What Do They Mean?

Eye doctors in Hamilton, NJ, explain common vision issues.

At some point in our lives, almost all of us experience at least some degree of floaters or flashing lights in our vision. As eye doctors, we tend to get questions about them often from our Hamilton and Princeton, NJ patients. There are various causes for these phenomena, and I will try to shed some light on this topic.

First I will start with flashes and floaters caused by problems within the eye and retina.

The inside of our eye contains a jelly called the vitreous. For most of us, there is debris within this jelly.  When light enters the eye, it hits this debris and casts a shadow on the retina, which in turn causes us to see floaters. This is a very benign condition, and although it can be annoying at times, it will not damage or harm our eyes or vision. There is also much variability from patient to patient with how noticeable these floaters are. Some patients will never notice them, while others see them constantly.

As we get a little older, the vitreous starts to contract and tugs on the retina. As it begins to tug, patients will often notice a flash of light. This flash usually lasts 1 or 2 seconds and is white in color. Eventually the vitreous will tug hard enough and separate from the retina, which is called a vitreous detachment. This leads to a different kind of floater and one that is usually larger and often looks like a circle or cobweb. This too can be very annoying but is harmless to our eyes. Over time, this floater will usually settle below our line of sight so we don’t see it as much. In certain cases, as the jelly separates from the retina, it will cause a rip or tear in the retina, which can lead to a retinal detachment. This is a more serious condition that requires prompt attention to prevent damage to the retina and vision loss. When this occurs, patients will typically notice more flashing lights, a greater number of floaters, and sometimes a veil or curtain over their vision.

In addition to flashes and floaters caused by problems to the retina, patients can experience these phenomena from other non-eye related conditions. Our eyes are an extension of the brain, so if something is disrupting the parts of the brain responsible for our vision, we can experience a number of different visual symptoms.

Transient ischemic attacks (TIAs), more commonly referred to as mini strokes, are an event in which the brain lacks proper oxygen for a timeframe of less than 24 hours. The most common cause for this is when an embolus, or blood clot, restricts the flow of blood to the brain. Depending of which part of the brain is affected, symptoms can include: weakness on one side of the body, difficulty speaking, confusion, and even visual symptoms such as loss of vision or flashing lights. There are even times when a patient can experience a mini stroke and have only these visual symptoms. Depending on where the blood clot is, these visual symptoms could affect one or both eyes. They can be described as a loss of vision, dimming of vision, or flashing lights. When patients see flashing light from a TIA or even a complete stroke, the flashes tend to last for minutes to hours, versus the retinal flashes that last for a few seconds as described earlier. This difference in duration of the flashes is important and helps to distinguish if the flashes are caused by something in the retina or brain.

In addition to mini strokes and strokes, flashes can also be a result of migraines. This type of flash is referred to as a migraine with “aura.” These flashes will often sparkle and grow in size then shrink. They will generally occur for minutes to an hour. Oftentimes, a headache will follow after the visual symptoms subside, but there are times where no headache will follow and the only symptoms are visual.

Typically, when patients come to see me complaining of flashing lights, the first concern they immediately think of is a retinal detachment. However, there are a number of different causes for flashing lights. My general advice to patients is to alert their eye care professional if they notice new flashes, floaters, or any changes to their usual floaters.

Do you have questions about floaters or flashes? Leave them for us in a comment.

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